Falling temperatures Wednesday signaled the major pattern change that will bring at least two weeks of wintry weather to the Rock Hill area and the rest of the eastern United States, forecasters say.
They say the new pattern will mean below-average temperatures for the Carolinas, heavy lake-effect snow in the Great Lakes, and the threat of a winter storm along the East Coast.
“This pattern is expected to persist through at least mid-December,” says meteorologist Brad Pugh, of the National Weather Service’s Climate Prediction Center in College Park, Md.
For the Rock Hill area, the change will come in stages, with the lowest temperatures this weekend. Forecasters expect temperatures to rebound slightly early next week before another surge of arctic air arrives late Tuesday.
In addition to the cold, a storm system forecast to develop along the Carolinas coast could bring some light snow or a rain-snow mix to areas north of Charlotte on Friday. The precipitation might end as snowflakes in the Rock Hill area late Friday night and early Saturday.
The new weather pattern is a huge trough – or dip in the jet stream – that will be shaped like the letter “U” and extend from the Mississippi River to the East Coast.
Pugh said there are indications that by Christmas, the coldest weather might shift back into the upper Midwest. But cooler-than-average readings are forecast for the East through December.
Temperatures in Rock Hill fell from the upper 50s shortly after midnight into the lower 50s by midday Wednesday. Cloudy skies and highs near 50 are forecast for Thursday.
By early Friday morning, forecasters say precipitation from the coastal low could spread inland to the Rock Hill area. With temperatures expected in the upper 30s and low 40s during the day Friday, anything that falls would be rain, according to meteorologist Sandy LaCorte of the National Weather Service office in Greer.
But with temperatures falling into the low 30s late Friday night, the rain might end as snow.
Clearing is forecast Saturday. Highs are expected to reach the upper 40s and the lower 40s Sunday. Afternoon readings in the low 50s are predicted to return Monday and Tuesday.